shifting hard

I have noticed in the last few days it is shifting vary hard into high gear, I am not sure if it is at torque converter lockup, or 3rd gear to 4th. Depending on acceleration it is between 38 and 50 mph.

Any ideas?

Thanks Jim

100 years from now it won't matter
What kind of car I drove,
What kind of house I lived in,
or How much money I made,
What will matter is that I was important in the life of a child.